When production becomes marginal in a given zone in a field, one way to bolster production is to inject large quantities of fluid such as water or steam into an injection well at one point in the zone or zones in question and take additional production in another well or wells in the field. In the injection well pumping equipment is used to move large amounts of fluid into the well to get the desired enhanced production. The injection well can have a valve, typically of a sliding sleeve design, to allow access into a single zone at a time and in turn service multiple zones, if desired. These sliding sleeve valves have a sleeve with a port where the port can be selectively brought into alignment with the housing around it. The injection well can have a service life as long as 15 years or more. In the course of its life span, high fluid volumes and large weights of entrained solids can be forced through a single sliding sleeve valve, when it is in the open position. It would not be unusual that in the life of such a well injection rates of about 45,000 barrels per day would be used. This could result in 250 million barrels pumped during the life of the well. Additionally, with solids content of about one pound per 1000 barrels the amount of solids pumped through such an opening could reach 250,000 pounds of fine sand, generally smaller than 50 micron and having a generally sharp and angular shape, being pumped through the open port in the expected life of the well.
Maintaining these rates over long periods has raised concerns about erosion of the opening in the tool and more significantly to the surrounding casing
In the past, other work has been done relating to crossover tools used in high rate high volume frac packing, as reported in the American Association of drilling Engineers (AADE) paper 03-NTCE-18 in 2003 by a group of engineers from Halliburton Energy Services Inc. In this application there are high flow volumes with significantly more solids content than in fluid injection applications. In the design tested in this paper, both the tool body and the sliding sleeve had matching ports that were created by simply angling a drill at a predetermined angle from the axis of the tool and drilling in an uphole direction through the tool body and the sleeve. This technique results in an oval shaped opening when viewed in a line perpendicular to the tool axis. The hole appears narrower at the top and bottom because of the slant in the drilling process and having generally parallel slopes at the uphole and downhole ends, again resulting from the slant drilling technique. While positive results were reported for high flows and high solids content application of frac packing, the overall volumes of fluid pale in comparison with the volumes of fluid and solids used during the life of an injection well.
As a result of these differences simulations (such as CFD, Computational Fluid Dynamic models or simulations were run to evaluate port effectiveness) and field tests have led to an improved port design to minimize erosive effects on the surrounding casing and to the ports themselves. The resulting port designs feature elongated openings that flare in the downhole direction. It further can feature a multi-sloped downhole outlet composed of ramps or/and curves. These and other features of the invention will be more readily appreciated by those skilled in the art from a review of the description of the preferred embodiment and the claims that appear below.